The present disclosure relates generally to electric machines and, more specifically, to a thermal conductor and methods for forming the thermal conductor for use in electric machines.
At least some known electric machines, such as electric generators and electric motors, may be fabricated in a variety of configurations and may be used in a wide array of applications. Electric machines generally produce energy through induced rotational forces and induced torque that are applied to a rotor shaft of the electric machine. Generally, electric machines generate heat during operation as a result of both electrical and mechanical losses. For example, heat may be generated by a process commonly referred to as Joule heating when current is applied through a stator winding of the electric machine during operation. The amount of heat generated by Joule heating is generally dependent on the amount of current applied through the stator wire, and the electrical resistance of the wire. Generally, the power density of an electric machine may correspond to the amount of heat generated therein. In at least some known electric machines, the greatest amount of heat is generated at the end-turns of the stator winding.
One known method of dissipating heat generated at the stator end-turns of an electric machine is to position a thermally conductive layer between the end-turns and the housing of the electric machine. At least some known thermal conductors are fabricated from a polyimide material, a fiberglass material, and/or a varnish material. However, polyimide-based thermal conductors generally have a low thermal conductivity that limits the heat dissipation from the end-turns. Another known method includes spray cooling a portion of the electric machine with a flow of dielectric cooling liquid. However, spray cooling requires the use of a complex system of components to supply the liquid to the electric machine.